Air tightness is one of the most important area of focus in residential construction. Many builders think that achieving an air tightness number that is low enough to surpass the codes needs requires a significant increase in budget due to costly materials
and increased labor. But you can follow some simple steps that can work nicely.
Air-sealing starts at the basement
The air barrier starts below ground level under the building – remember this very important concept. The code requires builders to use a 6-mil poly barrier, but you can move to a 10-mil poly, which will be applied directly over the under-slab insulation. The 10-mil thickness withstands traffic better than the code-required 6-mil and prevents
damage. During the installation all the seams are lapped and can be taped to ensure an airtight installation. When it’s available it is better to use a continuous piece of poly. If a passive radon vent needs to be installed be aware that this pipe has to go up to the roof, and this part of the job can be a leak area in the future.
Another option – but with additional costs for you – is to include some insulation in the basement floor. It can be a recycle option or common brand products that can be installed in 4″ x 8′ panels, mainly if you are planning a finish basement for some play room or office there.
Air-sealing the connection between the concrete and framing
An important area to be sealed is the connection between the concrete wall and the framing base. When it comes to sealing the sill plate to the slab you normally use the standard foam sill sealer required by code as a capillary break below the pressure-treated sill. You can also add two beads of sealant, but in our opinion is it important to add other sealants. The products are supposed to have a long service life and you have a lot of brands in the market.
Other concepts are very important also to complete your air sealing, and we will be discussing the concepts in other posts in the future